Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$194.33	12.837%	$219.2761	$219.28	$219.30	$219.30
Purchase #2	$25.95	8.515%	$28.1596	$28.16	$28.15	$28.20
Purchase #3	$80.36	10.835%	$89.067	$89.07	$89.05	$89.10
Purchase #4	$35.78	12.180%	$40.138	$40.14	$40.15	$40.10
Purchase #5	$215.68	8.557%	$234.1357	$234.14	$234.15	$234.10
Purchase #6	$199.46	6.817%	$213.0572	$213.06	$213.05	$213.10
Purchase #7	$54.62	8.255%	$59.1289	$59.13	$59.15	$59.10
7 purchase totals =	$806.18		$882.9625	$882.98	$883.00	$883.00